Doctor assembly

ABSTRACT

A DOCTOR IS DISCLOSED HAVING A PIVOTABLE DOCTOR BACK PARALLEL TO AND SPACED FROM A ROLL OF A PAPER MAKING MACHINE. A BLADE CARRIED BY A BLADE HOLDER IS RESILIENTLY CONNECTED TO THE DOCTOR BACK BY A THIN PLATE OF SUBSTANTIAL WIDTH AND SUFFICIENT LENGTH RELATIVE TO ITS THICKNESS SO AS TO BE RESILIENT AND SUPPLEMENT THE RESILIENCY OF THE BLADE FOR IMPROVED CONTOUR FOLLOWING AND PRESSURIZED SCRAPING OF THE ROLL. THE THIN PLATE, MADE UP OF SEVERAL SEGMENTS ABUTTING EACH OTHER ALONG EDGES NORMAL TO THE ROLL, EXTENDS THE FULL WIDTH OF THE ROLL AND COVERS THE SPACE BETWEEN THE ROLL AND DOCTOR BACK. THE BLADE HOLDER COMPRISES SEGMENTS WHICH OVERLAP THE PLATE SEGMENT, WITH ADJACENT BLADE HOLDER SEGMENTS HELD IN ALIGNMENT FOR BLADE INSERTION AND REMOVAL, BY AN OVERLAPPED PLATE SEGMENT.

D. B. DE NOYER Feb. 2, i 911 DOCTOR ASSEMBLY Filed Dec. 19, 1968 UnitedStates Patent Office 3,559,229 Patented Feb. 2., 1971 U.S. Cl. -25651 1Claim ABSTRACT OF THE DISCLOSURE A doctor is disclosed having apivotable doctor back parallel to and spaced from a roll of a papermaking machine. A blade carried by a blade holder is resilientlyconnected to the doctor back by a thin plate of substantial width andsuflicient length relative to its thickness so as to be resilient andsupplement the resiliency of the blade for improved contour followingand pressurized scraping of the roll. The thin plate, made up of severalsegments abutting each other along edges normal to the roll, extends thefull width of the roll and covers the space between the roll and doctorback. The blade holder comprises segments which overlap the platesegments, with adjacent blade holder segments held in alignment forblade insertion and removal, by an overlapped plate segment.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS I have copending patentapplications related to the type of apparatus disclosed herein andentitled Double Cantilever Supported Doctor Blade Ser. No. 785,200 andDoctor Blade Holding Assembly Ser. No. 785,198 which were both filedconcurrently with this application.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates generally to apparatus used in paper making machines and inparticular to doctors which are used to scrape pulp and water frombreast rolls in fourdriniers or forming cylinders in cylinder machines,

. wet broke and water from press rolls, and web crumbs from rolls anddrums in web drying assemblies.

Description of the prior art Arrangement for applying doctor blades tothe surfaces of rolls in paper making or calendering machinery have beendisclosed in many prior art patents beginning perhaps with U.S. Pat.242,753 of 1881. Although U.S. Pat. 2,191,366 of 1940 disclosedaflexible strip doctor blade yieldably held against a roll surface by aresilient blade holder, it remained for my own U.S. Pat. 3,387,317 of1968 to disclose a roll and a flexible strip doctor blade held in bladeholders for endwise insertion and removal along a path parallel to theroll, with resilient rods of substantial length connecting each bladeholder to a doctor back, so that the flexibility of the rodssupplemented the flexibility of the blade itself to provide improvedcontour following and uniform pressure characteristics of the blade onthe roll surface. As paper making machines have continued to becomelarger and wider rolls of 300 to 400 inches wide or more are now neededwhere rolls of substantially less width were used in the past. Continuedinnovation in the field of this invention is therefore necessary inorder to provide satisfactory doctoring of such large rolls. The objectsof the present invention such as are hereinafter set forth are thereforedirected to further improvements and advances in the state of the artillustrated by these prior art patents and in particular my own U.S.Pat. 3,387,317.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a doctor assembly with improved roll contour following andpressurized scraping characteristics.

Another object of the present invention is to provide a doctor assemblywith an improved cantilever support for a blade holder and blade, whichwill eliminate a need for preloading blade holders in order to insertblades and eliminate a need for protective covering structure such ashas been required with certain commercially popular prior art structuresincluding my own U.S. Pat. 3,387,317 in order to prevent water or crumbstraveling over the blade holder and landing back on the roll from whichsuch water or crumbs had been removed.

Another object of the present invention is to provide a new and improveddoctor assembly in which the segments of a segmented blade holding meansare maintained in alignment for blade insertion and removal.

According to a preferred embodiment of the present invention a doctorblade is carried by a blade holder which is in turn connected to adoctor back by a thin plate spring of substantial width and sufficientlength relative to its thickness so as to be resilient and supplementthe resiliency of the blade for improved contour following andpressurized scraping of the roll. The thin plate, made up of severalsegments abutting each other along edges normal to the roll, extends thefull width of the roll and covers the space between the roll and doctorback and the plate presents a flat continuous and imperforate surfacerequiring no protective cover. The blade holder comprises segments whichoverlap the plate segments, with adjacent blade holder segments held inalignment for blade insertion and removal, by an overlapped platesegment.

Other features and objects of the invention that have been attained willappear from more detailed description of the invention to follow withreference to an embodiment of the present invention shown in thedrawing.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing shows afragmentary perspective view of a paper making machine roll and doctorassembly according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing adoctor assembly 1 is provided with a doctor back 2 parallel to andspaced from a roll 3 of such as a paper making machine. The back 2 ismounted on means (not shown) to pivot about the axis 4. An actuatingmeans (not shown) is connected to the back 2 to selectively rotate theback clockwise or counterclockwise as indicated by the arrows 5 and 6.

The assembly 1 is provided with a resilient blade 10 extending along theentire width of roll 3 and having a first portion 11 of the blade, i.e.,its leading edge, engageable with the surface of roll 3. The blade 10has a second portion 12, i.e., its trailing edge, with a particularcross sectional configuration, in part thicker than the first portion 11of blade 10, for a purpose that will appear as this descriptionproceeds.

A blade holder assembly 15 is provided with a width corresponding to thewidth of blade 10. The blade holder assembly 15 comprises a plurality ofsegments 16 each having an upper jaw 17 and lower jaw 18. The jaws 17and 18 define a forward facing slot 20 and a rearward facing slot 21.The lower jaw 18 is provided with an upturned lip 22 for engaging thethicker part of the trailing portion 12 of blade 10. The blade 10 may beinserted into the cavity 20 by sliding the blade in slot 20 along a pathof movement parallel to the axis 4. The lip 22 prevents the bladefalling out of slot 20 toward roll. 3. The lip 22 also limits movementof the blade 10 relative to the blade holder assembly 15.

Resilient plate means 30 are provided to connect the doctor back 2 tothe blade holder assembly and project from the back 2 toward the roll 3as a flexible cantilever. The plate means 30 is an assembly of segments31. In order to provide for plate resiliency to supplement bladeresiliency in accordance with objects of this invention, the ratio ofthe plate length X to plate thickness Y is at least :1 and preferably ofthe order of 50:1 or more and the doctor back is located to accommodatesuch length. The width Z of the plate segments 31 is substantial,preferably, at least one-half of the plate length X, as the segments areassembled with adjacent edges 32, 33 abutting each to provide along withthe blade 10 and blade holder assembly 15, a cover over the entire spacebetween the doctor back 2 and roll '3.

The plate segments 31 may be attached to the doctor back 2 by anysuitable means and as shown in such means include a lower strip 40 andupper strip 41 defining a slot 42 for holding plate segments 31 andscrews 43 secure this assembly to the doctor back 2. The opposite end ofplate segments 31 is inserted into the rearward facing slot 21 definedin blade holder segments 16 and secured therein by bolts 44. Thesegments 31 of the plate means 30 and the segments 16 of the bladeholder assembly are arranged relative to each other to provide foradjacent edges 32, 33 of segments 31 being overlapped by a segment 16 ofthe 'blade holder assembly 15.

In the assembly and operation of the described apparatus, with the platesegments 31 attached to the doctor back 2 and the blade holder segments16 attached to the segments 31, the doctor back may be rotated aboutaxis 4 in the direction of arrow 5 to raise the blade holder assembly 15above roll 3 for convenient insertion or removal of blade 10. A blade 10can be inserted endwise, that is along a path of motion parallel to theaxis 4, into the slot 20 without preloading the blade holder segments16, as the overlapped and overlapping relationship between the platesegments 16 will maintain at all times the slot 20 in each holdersegment 16 in alignment for insertion of a blade 10. With a blade 10'inserted in slot 20, doctor back 2 may be rotated about axis 4 in thedirection indicated by arrow 6 until blade 10 contacts the surface ofroll 3 with a pressure such as may be selected by the machine opera:tor. With blade 10 making pressure contact with roll 3 the platesegments 31, covering the entire space between doctor back 2 and roll 3,is free to flex and this resiliency supplements the resiliency of theblade 10 to provide for improved performance in the blade following thecontour of roll 3 and applying pressure uniformly thereto across theentire width of roll 3.

From the foregoing detailed description of the present invention, it hasbeen shown how the objects of the invention have been attained in apreferred manner. However, modifications and equivalents of thedisclosed concepts such as readily occur to those skilled in the art areintended to be included within the scope of this invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A doctor assembly for a roll in a paper making machine, the doctorassembly comprising:

(A) a doctor back adapted for mounting in parallel spaced arrangement toa paper machine roll;

(B) a resilient blade having a first portion along the entire widththereof for engagement with the surface of the roll;

(C) blade holder means engaging and holding a second portion of theblade along the entire width thereof, said second portion being remotefrom and parallel to the first portion of the blade;

(D) resilient plate means connecting the doctor back to the blade holdermeans, said plate means providing a continuous imperforate surfacebetween the doctor back and blade holder means and of a widthcorresponding to the width of the roll;

(E) the doctor back being adapted for mounting at a location spaced fromthe roll a distance that provides the plate means between the back andthe blade holder means with a cantilevered span projecting from the backtoward the roll of a dimension having a ratio to the thickness of theplate means of at least 20:1 to provide a resiliency theretosupplementing the resiliency of the blade for contour followingengagement of'the blade with the roll; and in which (F) both the bladeholder means and the resilient plate means are assemblies of segmentseach arranged with abutting edges of adjacent segments being transverseto a central axis through the roll, and the segments of the blade holdermeans are arranged to locate a segment of the blade holder inoverlapping relation to each pair of abutting edges of adjacent platemeans segments whereby the segments of the plate means maintain thesegments of the blade holder means in alignment for insertion andremoval of the blade in the blade holder means.

References Cited UNITED STATES PATENTS 1,561,513 11/1925 Frossard15256.5l

1,696,119 12/1928 Heisel 15-256.51

2,191,366 2/1940 Buccicone et al. 15-256.51

FOREIGN PATENTS 287,565 5/ 1929 Great Britain 34--12O WALTER A. SCHEEL,Primary Examiner L. G. MACHLIN, Assistant Examiner

